In a vehicle, a lot of electronic control units (ECUs) controlling various controlled plants (controlled objects) such as an engine, a power steering, a brake, and a torque converter are installed.
In the development phase and the design phase of the ECUs as mentioned above, a simulator which is called so-called HILS (Hardware In the Loop Simulation) and simulates responses equal with a real engine is used on behalf of each controlled plant such as the real engine (see Reference 1, for example).
The HILS includes an interface unit for inputting and outputting a signal from/to the ECU.    [Reference 1] Japanese Unexamined Patent Publication No. 2004-361292